Composite Housing with a Metallic Flange for the Compressor of an Axial Turbomachine

ABSTRACT

The present application relates to an annular outer housing of a low-pressure compressor of an axial turbomachine. The housing includes an annular wall of a composite material with an organic matrix. The housing includes an annular array of blades extending radially, the blades including platforms fixed to the annular wall. The housing also includes a radial annular flange having means of mounting configured to allow fitting of the housing in the turbomachine. The annular flange is attached to the annular wall and bounds an annular insertion area for the platforms of the blades. The annular flange is fixed on the annular wall by means of clamping. The present application reduces the manufacturing cost of the housing and supports the transmission of force between the annular flange and the blade platforms, which has the advantage of reducing stresses in the annular wall.

This application claims priority under 35 U.S.C. §119 to European Patent Application No. 13170209.4, filed 3 Jun. 2013, titled “Composite Housing with a Metallic Flange for the Compressor of an Axial Turbomachine,” which is incorporated herein by reference for all purposes.

BACKGROUND

1. Field of the Application

The present application relates to the housing of an axial turbomachine. More particularly, the present application relates to an annular compressor housing for an axial turbomachine made of a composite material and supporting an annular row of blades.

2. Description of Related Art

In order to reduce the weight of an aircraft turbojet engine, some components are made of composite materials. In particular, a structural component such as an external annular housing may be made of composite material. Such a housing, in addition to supporting the rows of stator blades, is generally used for mounting other structural engine components. It must therefore have adequate mechanical strength.

In the case of a low-pressure compressor housing, the housing is in contact with the splitter nose. However, the latter is liable to ingest foreign objects. The housing must therefore have some flexibility and resilience in order to be able to distort and withstand impacts without breaking.

The blades which are fixed to the housing may be fixed through platforms pinned against the inner surface of the housing. The blades are subjected to forces related to the flow of the stream and transmit loads which the housing must withstand. In addition, the housing must withstand forces from the means of fixing for securing the blades as well as any resultant stress concentrations. It should be emphasized that the housing is commonly in contact with several sets of means of fixing which also generate stress concentrations.

Patent EP 2402615 A1 discloses an external compressor housing for an axial turbomachine. The housing includes an annular wall and two radial flanges, one upstream and the other downstream. The housing is made of a composite material. It supports multiple annular rows of stator blades. Each blade has an outer platform which is secured to the annular wall by means of fixing.

It is standard practice that the radial flanges are attached to the splitter nose and an intermediate housing of the turbomachine. This may be achieved by inserting bolts in holes drilled in the radial flanges. These holes are particularly stressed when the engine is in operation and pull-outs may occur due to mechanical clamping forces and/or vibration.

To counteract these pull-outs, it is possible to substantially thicken the flanges. However, this solution tends to increase the weight of the housing, thus reducing the expected weight saving resulting from the use of a composite solution. Furthermore, the mechanical strength of this solution is limited and stress concentrations remain.

In order to strengthen the wall, it is standard practice to construct an annular housing with a composite wall and metal radial flanges.

Patent FR 2282537 A1 discloses a compressor with an external housing of an axial turbomachine. The housing comprises annular rows of blades as well as alternating annular spacers and blade-retaining rings. The retaining rings are made of metal and are shrunk into the annular spacers. These are made of light metal to resist mechanical stresses. The housing accommodates a composite annular wall which surrounds the retaining rings and the annular spacers. The composite wall is made on a mandrel onto which the rings and spacers are fitted. The use of the mandrel represents a significant cost, both in terms of equipment and manpower. The time to wind the continuous filament onto the mandrel is expensive in manufacturing time. Although this housing comprises composite material, it remains heavy because of its metal components. Furthermore, the method of fixing the blades is complex. It is based on a plurality of mechanical interfaces requiring costly adjustments.

Although great strides have been made in the area of axial turbomachines, many shortcomings remain.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an axial turbomachine in accordance with the present application.

FIG. 2 shows a diagram of a turbomachine compressor in accordance with the present application.

FIG. 3 illustrates an axial section of part of the housing in accordance with a first embodiment of the present application.

FIG. 4 illustrates an axial section of part of the housing in accordance with a second embodiment of the present application.

FIG. 5 is a view from the inside an annular flange in accordance with the second embodiment of the present application.

FIG. 6 illustrates a blade platform in accordance with the second embodiment of the present application.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present application aims to solve at least one of the technical problems presented by the prior art. More specifically, the present application aims to reduce the cost of producing a composite housing. The present application also aims to reduce the mechanical stresses in the composite annular wall of a turbomachine housing.

The present application relates to a housing of an axial turbomachine, especially a compressor, comprising an annular wall made of a composite material whose inner surface comprises an annular area in which a row of blade platforms which extend radially are inserted, at least one annular attachment flange extending radially, wherein the annular flange is attached to the annular wall and bounds the blade platforms insertion area.

The term annular flange attached to an annular wall means an annular flange fixed on the annular wall, for example, by means of fixing.

According to an advantageous embodiment of the present application, the radial section of the annular flange has an L-shaped profile, the profile having an axially extending part and a radially extending part, the axially extending part preferably being located mainly radially on the side of the inner surface of the annular wall, and the radially extending part being located mainly radially on the side of the outer surface of the annular wall.

According to an advantageous embodiment of the present application, the axially extending part of the flange comprises an edge bounding the annular blade platforms insertion area.

According to an advantageous embodiment of the present application, the annular wall comprises an annular area for inserting an abradable material, the insertion area of the platforms being bounded, on the one side, by the said insertion area of a material abradable and, on the other, by the edge of the axially extending part of the flange.

According to an advantageous embodiment of the present application, the blade platforms insertion area forms an annular recess, the radial section of the annular recess preferable being substantially rectangular and designed to permit radial insertion of the blade platforms.

According to an advantageous embodiment of the present application, the annular wall and the annular flange are made of different materials, the annular flange preferably being made of a metallic material.

According to an advantageous embodiment of the present application, the composite annular wall comprises an organic matrix and a preform comprising fibres, the matrix preferably being homogeneously distributed over the annular wall.

According to an advantageous embodiment of the present application, the annular wall comprises a first means of fixing, the annular flange includes a second means of fixing and the blades comprise a third means of fixing, the first means of fixing aligning with the second means of fixing, and/or the third means of fixing aligning with both the first means of fixing and the second means of fixing.

According to an advantageous embodiment of the present application, the third means of fixing extend radially through the annular wall and the annular flange; the third means of fixing preferably comprising clamping means, possibly reversible.

According to an advantageous embodiment of the present application, the contour of each platform has longitudinal and transverse edges, at least one of the said edges being in contact with the annular flange, the flange thus ensuring that the platforms are locked against rotating.

According to an advantageous embodiment of the present application, the platforms and the annular flange each comprise a guidance surface designed to guide the flow in a turbomachine, the guidance surfaces of the platforms lying flush with the guidance surface of the annular flange.

According to an advantageous embodiment of the present application, the annular flange comprises a part which follows a surface, preferably interior, of the annular wall, the said part extending axially over the majority of the blade platforms insertion area.

According to an advantageous embodiment of the present application, the annular flange has radial recesses for inserting the blade platforms, the radial recesses preferably being designed to be largely open towards the bodies of the blades.

According to an advantageous embodiment of the present application, the housing comprises an annular row of blades with platforms, each of which has a generally disc-shaped central region, and two areas of reduced thickness located axially on either side of the central area, the central area predominantly bearing radially against the annular flange and at least one of the areas of reduced thickness abutting predominantly axially against the annular flange.

According to an advantageous embodiment of the present application, the means of fixing may include pins, preferably threaded, and can include means of clamping.

According to an advantageous embodiment of the present application, the means of fixing are reversible means of fixing.

The radial section of the annular flange is a section along a plane that includes a radial axis and the axis of rotation of the turbomachine.

According to an advantageous embodiment of the present application, the compressor is a low-pressure compressor.

According to an advantageous embodiment of the present application, the housing is an external housing designed to guide an axial flow.

According to an advantageous embodiment of the present application, the housing comprises two half-shells split along a longitudinal plane.

The longitudinal plane means a plane passing through the axis of rotation of the turbomachine.

According to an advantageous embodiment of the present application, the housing comprises a plurality of annular rows of blades, preferably at least three.

According to an advantageous embodiment of the present application, the housing is a compressor housing comprising a plurality of annular rotor blade rows, the housing surrounding the majority of the rotor blade rows.

According to an advantageous embodiment of the present application, the annular wall comprises a curved surface of revolution, the surface of revolution being preferably curved outwards.

According to an advantageous embodiment of the present application, the annular wall is formed by injecting resin into a mould in which a preform is enclosed.

According to an advantageous embodiment of the present application, the means of fixing to the annular wall comprise holes.

According to an advantageous embodiment of the present application, the first means of fixing comprise a first set of means of fixing arranged annularly and axially overlapped by the annular flange, and a second set of means of fixing arranged annularly and overlapped axially by the platforms, the axial spacing between the first set and the second set being less than the axial length of the platforms.

According to an advantageous embodiment of the present application, the wall is mostly non-metallic.

According to an advantageous embodiment of the present application, the wall is preferably uniquely made of a matrix and fibres.

The majority of the wall is defined by its mass or its volume.

According to an advantageous embodiment of the present application, the density of the wall is less than 4.00 mm, preferably less than 2.50 mm, more preferably less than 1.00 mm.

According to an advantageous embodiment of the present application, the annular flange is made of titanium, aluminium or steel.

According to an advantageous embodiment of the present application, the annular flange extends mainly radially in a direction opposite to that of the blades with respect to the annular wall.

According to an advantageous embodiment of the present application, the fixing holes of the annular flange are located in the radial recesses.

According to an advantageous embodiment of the present application, the annular flange has a junction part between the radial part and the axial part.

According to an advantageous embodiment of the present application, the annular flange has an axial extension extending axially from the junction part to the axis of the bearing plane of the radial part.

According to an advantageous embodiment of the present application, the bottom of each radial recess comprises a central part and two side parts located laterally in line with the central part, the side parts being inclined to the central part towards the exterior of the corresponding recess.

According to an advantageous embodiment of the present application, the radial recesses are separated from each other circumferentially.

According to an advantageous embodiment of the present application, the radial part has means of assembly such as mounting holes which extend generally axially.

According to an advantageous embodiment of the present application, the radial part has a bearing surface perpendicular to the axis of rotation of the turbomachine.

According to an advantageous embodiment of the present application, the junction part has a rectilinear surface and is inclined relative to the radial part and relative to the axial part, at which point the profile of the junction part forms a step, the junction part preferably being step-shaped, having a cylindrical face designed to ensure a shaft-bore fit.

According to an advantageous embodiment of the present application, the preform comprises a stack of carbon and/or glass fibre sheets, the number of sheets possibly being the same over the entire surface of the preform.

According to an advantageous embodiment of the present application, the fibres are longer than 3.00 cm, more preferably longer than 6.00 cm, even more preferably longer than 12.00 cm.

According to an advantageous embodiment of the present application, the blades are located in stator segments with common platforms.

The present application also relates to an axial turbomachine comprising a housing, wherein the housing is in accordance with the present application, the housing preferably being an external annular housing and comprising an annular flange upstream and an annular flange downstream.

The present application leads to a reduction in the production cost of the composite housing with a metal flange. It puts forward a modular composite housing since it enables different components to be manufactured separately. This technology also simplifies any repairs in the future.

The present application reduces the mechanical stresses in the annular wall of the housing. The present application allows some of the forces on the surfaces of the blade platforms to be distributed, the distribution being direct or indirect. The present application offers an additional interface between the blade platforms and the flange; this constitutes a force transmission route which locally bypasses the edge of the annular wall.

The present application uses an annular flange with a material different from that of the annular wall. The material of the blade platforms is also different from that of the annular flange. These features offer a choice of materials having different strengths and different compactness. Thus, it is possible to lighten some parts while strengthening others. The balance between mass and mechanical strength can be determined independently for the different interfaces.

The present application reduces the number of sheets in the composite preform by reducing mechanical stresses. One consequence is that the preform is easier to manufacture because the difficulty of using sheets tends to increase for each additional sheet. This difficulty is compounded by the curved surfaces that current housings have. Savings are made in the costs of material and the labour associated with the preform.

In the following description, the terms inner or internal and outer or external refer to a position relative to the axis of rotation of an axial turbomachine.

FIG. 1 shows a schematic view of an axial turbomachine. In this case it is a double-flow turbojet. The turbojet 2 comprises a first compression stage, a so-called low-pressure compressor 4, a second compression stage, a so-called high-pressure compressor 6, a combustion chamber 8 and one or more turbine stages 10. In operation, the mechanical power of the turbine 10 is transmitted through the central shaft to the rotor 12 and drives the two compressors 4 and 6. Reduction mechanisms may increase the speed of rotation transmitted to the compressors. Alternatively, the different turbine stages can each be in communication with the compressor stages through concentric shafts. These latter comprise several rotor blade rows associated with stator blade rows. The rotation of the rotor around its axis of rotation 14 generates a flow of air and gradually compresses it up to the inlet of the combustion chamber 10.

An inlet fan, commonly designated a fan 16, is coupled to the rotor 12 and generates an airflow which is divided into a primary flow 18 passing through the various above-mentioned levels of the turbomachine, and a secondary flow 20 which passes through an annular conduit (shown in part) along the length of the machine and then rejoins the main flow at the turbine outlet. The primary flow 18 and secondary flow 20 are annular flows and are channelled through the housing of the turbomachine. To this end, the housing has cylindrical walls or shells that can be internal or external.

FIG. 2 is a sectional view of an axial turbomachine compressor. The compressor may be a low-pressure compressor 4 such as that of FIG. 1. Shown are a part of the fan 16 and the splitter nose 22 for the primary flow 18 and secondary flow 20. The rotor 12 comprises several rows of rotor blades 24, in this case three.

The compressor 4 includes several stators, in this case four, each containing a row of stator blades 26. Stators are associated with a fan 16 or a row of rotor blades for straightening the airflow so as to convert the velocity of the stream into pressure.

The stator blades 26 extend essentially radially. They are equidistant from each other, and have the same angular orientation to the airflow. Advantageously, the blades 26 in one row are identical. Optionally, the spacing between the blades can vary locally as can their angular orientation. Some blades in a row may be different from the rest.

The stator blades 26 each have an airfoil or body also extending radially through the main air flow 18. Each blade also comprises at least one platform, optionally two platforms, that is an external platform 28 and an internal platform. The platforms bound the primary flow radially. They comprise guidance surfaces designed to guide the said flow.

The compressor has an external annular housing 30. The housing 30 encloses the compressor. To this end it has an annular wall 32 surrounding a majority of the rotor blades 24. The annular wall 32 may be formed of two half shells each forming half of a tube cut axially. The annular wall 32 is barrel- or ogive-shaped. Its interior face is concave. Its change in radius is continuous in order to compress the flow gradually.

The external housing 30 is fixed upstream to the splitter nose 22, and is fitted into the intermediate housing 34 of the turbomachine downstream. The intermediate housing 34 comprises an inner annular wall and an outer annular wall between which extend an annular row of blades or arms of the housing. The housing is essentially, preferably only, connected to the splitter nose 22 and the intermediate housing. The splitter nose 22 can be fixed only to the external housing 30 so as to be its only means of support.

The external housing 30 also includes an annular radial flange, preferably two annular flanges 36. The external housing 30 is fixed to the splitter nose 22 and the intermediate housing 34 by means of its annular flanges 36. The external housing 30 comprises an upstream annular flange and a downstream annular flange. Each of them can be semicircular. Preferably, each semicircle coincides with a half shell of the external housing 30.

The external housing 30 also comprises annular layers of abradable material 38. These abradable layers 38 are located axially at the rotor blades 24. They extend axially between the outer platforms 28 of the stator blades 26.

FIG. 3 is a view of an external housing 30 of the compressor section of an axial turbomachine 2 such as that of FIG. 1. The teaching of the present application could also be applied to a turbine housing, a combustion chamber or to an intermediate housing. The housing may be an exterior housing or an interior housing that respectively bounds the exterior or the interior of an annular flow. The housing shows one of the stator blades 26 and part of the annular flange 36.

The annular wall 32 comprises a first means of fixing. The first means of fixing may comprise through holes forming at least one annular row. The first means of fixing may comprise a first set of means of fixing arranged annularly and a second set of means of fixing arranged annularly. The first set is axially overlapped by the annular flange, the second set being axially overlapped by the platform. The first means of fixing may comprise other sets of means of fixing which overlap with one another and mate with another annular radial flange and/or with other annular rows of blades.

The annular wall 32 is made of a composite material. The composite material may comprise an organic matrix. The matrix may be made from an organic resin injected into a mould in which it then cures. The injection process can be a transfer process, Resin Transfer Moulding, known by the acronym RTM. Preferably the resin is thermosetting. It can be an epoxy resin.

The composite material comprises a preform. The latter may be formed from a stack of plies or sheets of fibres. The sheets may be sheets with glass fibres and/or carbon fibres. The fibres are long fibres. The fibres can be ordered and/or randomly arranged. The fibres may be woven. They may be pre-impregnated with a resin. The preform comprises a stack of 5 to 40 sheets, preferably from 8 to 20 sheets, more preferably 10 to 15 sheets. The number of layers formed by the sheets may vary locally so as to locally reinforce the housing, for example at fixing points.

The annular flange 36 is made of a different material from the annular wall 32. It can be made of a metallic material. It can be made of titanium, aluminium or steel. The annular flange may be made of a composite material, for example with a ceramic matrix and/or with metal fibres. The matrices and the fibres described above may also be used.

The annular flange 36 has a generally L-shaped profile. The profile has a radial part 40 and an axial part 42. The profile has a generally constant thickness, the thickness varying by less than 20% of its average thickness. The axial part 42 can be inclined relative to the axis of rotation of the turbomachine. The axial part 42 has a bearing surface matching the inner surface of the end of the annular wall 32.

The inner surface of the annular wall 32 comprises an annular insertion area 43 for the platforms of the blades 26. The annular insertion area 43 can have a radial profile that is rectangular or substantially trapezoidal so as to allow insertion of the platforms from the interior. The annular flange 36 can directly bound the annular insertion area 43. Preferably, it is part of the axial part 42 which bounds the annular insertion area 43. For this purpose, it has an annular upstream edge 44 which bounds the insertion area 43. The annular wall 32 comprises an annular insertion area for an abradable material 37. The insertion area 43 of the platforms may be bounded by the annular insertion area for an abradable material 37. It may also be bounded by the edge 44 of the axially extending part of the flange 42. Advantageously, the annular layer of abradable material 38 is housed in the annular insertion area for an abradable material 37.

The annular flange 36 is fixed to the end of the annular wall 32 through its axial part 42. This latter has for this purpose second means of fixing 45 which mate with the first means of fixing of the wall. The second means of fixing 45 may be axes extending generally radially, preferably orthogonal to the interface between the annular wall 32 and the axial part 42. The axes may be lockbolts or screws. They are mounted on the annular flange once it is pressed against the annular wall.

The radial part 40 of the profile of the annular flange 36 generates, by rotation about the axis of rotation 14, a plane 46 perpendicular to the same axis. Means of mounting 48 can be located on the radial part 40. The means of mounting 48 may be apertures for inserting screws aligned with the intermediate housing. The spacing between the second means of fixing 45 can be closer than that of the means of mounting 48.

The profile of the annular flange optionally comprises a junction part 50 between the axial part 42 and the radial part 40. The junction part 50 may be step-like. The shape of the step may be machined to provide axial clearance 52 at the axial end of the annular wall 32. The clearance 52 may be zero so as to provide support. Preferably the step shape projects outwardly. The inner surface of the junction part 50 may generate a rotating cylindrical surface 54. This cylindrical surface 54 can be a shaft-bore fit with the splitter nose, the intermediate housing, or any other element to which the annular flange 36 is fixed.

The blade 26 includes a third means of fixing 56 for attaching it to the annular wall 32. The third means of fixing 56 aligns with the first means of fixing of the annular wall. The third means of fixing 56 extends radially from the platform 28 in a direction opposite to the airfoil of the blade 26. The third means of fixing 56 may pass through the annular wall 32. The platform 28 generally follows the inner surface of the annular wall. The platform comprises a bearing surface which is usually pressed against the annular wall, optionally only the edge of the bearing surface is in contact with the annular wall.

The platform 28 is in contact with the axial part 42 of the annular flange. They abut axially against each other. Since the annular wall is slanted at this point, the platform and the axial part of the annular flange also enable the transmission of forces in a radial direction. The annular flange and the annular wall are in contact at the axial part 42. This contact area is extended and also allows transmission of axial and radial forces.

The junction 58 between the axial part 42 and the platform 28 is smooth. At this point, the thickness of the axial part and the annular flange are equal, so as not to disrupt the flow. To avoid there being any overlap, the line of the interface is perpendicular to the surface of the annular wall. The two elements are in contact over their entire thickness to facilitate the transmission of forces.

FIG. 4 illustrates a housing 130 in accordance with a second embodiment of the present application. FIG. 4 has the same numbering scheme as in previous figures for the same or similar elements, but the numbering is incremented by 100. Specific numbers are used for items specific to this embodiment.

The junction part 150 has a straight profile. The profile of the junction part is inclined relative to the profiles of the axial part and radial part. The length of the axial part 142 is greater than the length of the platform 128. The axial part overarches the platform upstream and downstream.

The annular flange 136 has a radial recess 160 in which the platform 128 of the blade 126 is inserted. The radial recess 160 may be formed on the inner surface of the axial part when the latter is placed inside the annular wall. In another configuration, the radial recess 160 may be formed on the outer surface if the axial part is outside the annular wall. The blade 126 is mounted on the annular flange 136 by inserting its platform 128 in the radial recess 160 from the inside.

The platform 128 has a central area 162 the fits against the bottom of the radial recess 160. It also has areas of reduced thickness 164 located axially on either side the central area 162. The areas of lesser thickness 164 may be recessed from the bottom of the radial recess 160.

In this configuration, the third means of fixing 156 of the blade, the second means of fixing of the annular flange, and the first means of fixing of the annular wall are aligned. The third means of fixing 156 is aligned with both the first means of fixing and second means of fixing. The holes formed in the annular flange and the holes formed at the ends of the annular wall are aligned. The fixing pin 156 of the blade passes through the fixing hole of the annular wall and the fixing hole in the annular flange. This solution simplifies assembly of the housing 130 as the third means fixing of the blades are used to fix both the annular flange and the annular wall. This reduces the weight of the housing. Savings in the means of fixing means is achieved. The housing is assembled more quickly.

The annular flange 136 also has an axial extension 166. The axial extension 166 extends from the junction part 150 in an opposite direction to the axial part 142. The axial extension may extend right up to the downstream surface of the radial part 140. It can serve as an axial end stop.

FIG. 5 shows the guidance surface of the annular flange in accordance with the second embodiment of the present application.

The annular flange 136 shows a plurality of radial recesses 160. The radial recesses are arranged annularly. They are spread over the inner surface of the annular flange 136. The radial recesses 160 are identical. They each have a second means of fixing. A platform 128 of a blade 126 is shown inserted into a radial recess.

Each radial recess 160 houses a blade platform 128. The length of the radial recess is adjusted to the length of the platform so that the platform is wedged axially in the housing.

The bottom of each radial recess 160 has a central part 168 and two side parts 170 arranged along the axial extension of the central part 168. These parts are planar. Each side part is inclined relative to the central part towards the exterior of the corresponding recess.

FIG. 6 illustrates a platform 128 of a blade 126 in accordance with the second embodiment of the present application. Optionally, this platform model can be used in other embodiments of the present application.

The platform 128 has a generally rectangular shape. It has two opposite longitudinal sides 172 lying along the axis of rotation of the turbomachine, and two opposite transverse sides 174 lying perpendicular to the axis of rotation of the turbomachine.

The central part 162 of the platform is generally disc-shaped. The disc may be truncated, possibly by the two longitudinal sides 172. The third means of fixing 156 are preferably centred on the central part 162. Making a platform with a reduced bearing surface reduces the rubbing surface between the platform and the annular flange. This facilitates the angular positioning of the blade. Also, the areas of reduced thickness 164 enable the blade to be made lighter. 

I Claim:
 1. A housing for a compressor of an axial turbomachine, comprising: an annular wall of composite material, the inner surface of which comprises an annular area for inserting platforms of a row of blades which extend radially; and at least one annular flange extending radially; wherein the annular flange is attached to the annular wall and bounds the insertion area of the platforms of the blades.
 2. The housing in accordance with claim 1, wherein the radial section of the annular flange is generally L-shaped, the profile thereof having an axially extending part and a radially extending part, the axially extending part being located mainly radially on the side of the inner surface of the annular wall, and the radially extending part being located mainly radially on the side of the outer surface of the annular wall.
 3. The housing in accordance with claim 2, wherein the axially extending part of the flange comprises: an edge bounding the insertion area of the blade platforms.
 4. The housing in accordance with claim 3, wherein the annular wall comprises: an annular area for inserting an abradable material, the insertion area of the platforms being bounded, on the one side, by the insertion area of the abradable material and, on the other, by the edge of the axially extending part of the flange.
 5. The housing in accordance with claim 1, wherein the insertion area of the platforms of the blades forms an annular recess, the radial section of the annular recess being substantially rectangular and designed to permit radial insertion of the platforms of the blades.
 6. The housing in accordance with claim 1, wherein the annular wall and the annular flange are made of different materials, the annular flange being made of a metallic material.
 7. The housing in accordance with claim 1, wherein the composite annular wall comprises: an organic matrix and a preform comprising fibres, the matrix being homogeneously distributed over the annular wall.
 8. The housing in accordance with claim 1, wherein the annular wall comprises a first means of fixing, the annular flange comprises a second means of fixing, and the blades comprise a third means of fixing, the first means of fixing aligning with the second means of fixing, and/or the third means of fixing aligning with both the first means of fixing and the second means of fixing.
 9. The housing in accordance with claim 8, wherein the third means of fixing extend radially through the annular wall and the annular flange, the third means of fixing comprising clamping means, possibly reversible.
 10. The housing in accordance with claim 8, wherein the clamping means are reversible.
 11. The housing in accordance with claim 1, wherein the contour of each platform includes longitudinal edges and transverse edges, at least one of the edges being in contact with the annular flange, the flange thus ensuring the platforms are locked against rotating.
 12. The housing in accordance with claim 1, wherein the platforms and the annular flange each comprise a guidance surface designed to guide the flow in a turbomachine, the guidance surfaces of the platforms lying flush with the guidance surface of the annular flange.
 13. The housing in accordance with claim 1, wherein the annular flange comprises: a part which follows an interior surface of the annular wall, the part extending axially over the majority of the insertion area of the platforms of the blades.
 14. The housing in accordance with claim 1, wherein the annular flange includes radial recesses designed for the insertion of platforms of the blades, the radial recesses being configured to be largely open towards the bodies of the blades.
 15. The housing in accordance with claim 1, wherein each platform includes a generally disc-shaped central region, and two areas of reduced thickness located axially on either side of the central area, the central area predominantly bearing radially against the annular flange and at least one of the areas of reduced thickness abutting predominantly axially against the annular flange.
 16. An axial turbomachine, comprising: a housing having an annular wall of composite material, the inner surface of which comprises an annular area for inserting platforms of a row of blades which extend radially, and at least one annular flange extending radially; wherein the annular flange is attached to the annular wall and bounds the insertion area of the platforms of the blades; and wherein the housing forms an external annular housing and comprises: an annular flange upstream; and an annular flange downstream. 